It is well known in modern copier/duplicators that operate on an electrographic process to locate a document at an exposure station and illuminate the document with a relatively high intensity lamp to thereby form a latent image of the document on a charged photoconductor. The image is then developed, transferred to a copy sheet and fused to that sheet. Some such copier/duplicators hold the document sheet stationary on a platen at the exposure station and illuminate the document by flashing one or more high intensity flash lamps. By using flash lamps capable of providing a high intensity, short duration pulse of illumination, a good latent image can be obtained even though the photoconductor is moving and the document is stationary at the time the lamps are flashed. In order to increase the copying rate, it is necessary for the photoconductor to be moved at a faster speed. Increasing the speed of movement of the photoconductor may result in blurred images on the photoconductor unless there are other changes in the process. One way to avoid blurring of the images is to reduce the time interval during which the flash lamps are illuminated, and this requires a lamp capable of producing a high intensity flash. The flash from high intensity lamps may annoy a machine operator when a document is placed directly on the platen without a platen cover being positioned over the document to shield the operator from the illumination produced by a high intensity flash. In addition, the use of a cover may be necessary in some countries in order to comply with governmental regulations. Thus the problems associated with high intensity illumination make it desireable to provide an auxiliary platen cover.
The use of simple hinged platen covers has been known for many years. It also is known to provide a foldable cover that is hinged at the rear edge of the platen and moveable from a folded position adjacent the platen to an extended position over the platen for covering a document located over the platen. Such a foldable platen cover is disclosed in U.S. Pat. Nos. 3,630,620 and 2,198,251.
Platen covers have not been used when the copier/duplicator is provided with a document feeder for automatically delivering documents to the platen or exposure station. Platen covers are not used with feeders because the document feeder typically overlies the platen or exposure station during operation of the feeder and therefore provides the desireable light shield. However, even the presence of such a document feeder on a copier does not entirely solve the problem because such feeders commonly are hinged for movement from an operating position overlying the platen to an elevated position spaced from the platen so that books or other documents can be placed directly on the platen for copying. For example, the before-mentioned co-pending U.S. patent application Ser. No. 427,237 discloses the mounting of such a feeder along the left side edge of a platen. When the feeder is in its elevated position, the operator can be exposed to high intensity flash lamps in the copier/duplicator and may experience some annoyance or discomfort. For a thin document, such as a sheet of paper, the feeder can be lowered over the document and thus function as a cover. However, for thick documents, such as a book, the feeder may not be effective to protect the operator completely from high intensity illumination.
Various types of document feeders also are known. In some instances, the document feeders comprise recirculating feeders in which document sheets of a set are fed seriatim from a supply to the platen for copying once and then returned to the supply. The set of document sheets is recirculated one or more times in order to obtain one or more sets of copies. In other instances, semi-automatic document handlers or feeders receive a single document sheet manually fed by an operator and deliver such sheet to the platen for copying one or more times. Then the operator delivers a second sheet for copying one or more times. If the various document sheets are related, the resulting copies must be collated manually or directed into separate collator apparatus. Such semi-automatic document handlers are referred to herein as document positioners.
It also is known to provide a combination recirculating document feeder and document positioner. In this regard, reference is made to the commonly assigned U.S. Pat. No. 4,176,945 entitled SHEET FEEDING APPARATUS FOR USE WITH COPIER/DUPLICATORS OR THE LIKE, which issued on Dec. 4, 1979 in the names of R. C. Holzhauser, C. H. Zirngibl and V. J. O'Brien. The present invention is especially useful in connection with a combination recirculating feeder, document positioner, as generally disclosed in such U.S. Pat. No. 4,176,945, and with the beforementioned document positioner type feeder.
Sheet guide members have been provided for registering a sheet before manually advancing the sheet into a document positioner. For example, the Kodak Ektaprint 250 Duplicator, manufactured by the assignee of the present application, has two such sheet guide members on the upper surface thereof adjacent to the inlet to the document positioner. The guide members of the Ektaprint duplicator are adjustable relative to each other by an operator grasping one of the guide members and moving it toward or away from the other guide member. Sheet guide members for feeding document sheets in duplicator apparatus or the like also are disclosed in commonly assigned U.S. Pat. No. 4,245,831 which issued on Jan. 20, 1981 in the name of S. F. Michatek, and in U.S. Pat. Nos. 2,197,036 which issued on Apr. 16, 1940 in the name of F. R. Ford, 2,233,895 which issued on Mar. 4, 1941 in the name of L. Mestre, and 3,339,916 which issued on Sept. 5, 1967 in the name of J. L. Tregay.
Thus the art generally has recognized the problems associated with high intensity flash illumination of documents at an exposure station. However, the usual solution of providing a cover for the exposure station, while adequate in some instances, does not solve the problem when document feeders normally cover the exposure station but are lifted for copying of individual document sheets, books or the like. In the latter instance the document feeder typically takes up a substantial amount of room and frequently is mounted at the rear on the platen in such a way that little or no room is available for a cover when the feeder is raised for copying individual documents.